WASHINGTON – The fireworks on July Fourth were great, but they can’t compete with the show my wife and I have been enjoying for hours every evening over the past couple of weeks: the biggest display of firefly fireworks either of us can remember.

These bio-luminescent, winged wonders are creatures of moisture. The wet and humid conditions we humans are barely able to endure have helped their populations explode, especially in pesticide-free areas.

A plethora of lightning bugs now means we will soon have the opportunity to catch a glimpse of the glowworm — the larval, wingless form of the firefly. Look for their flashing lights on the ground in late summer, and then again next spring. Glowworms are highly beneficial, eating lots of the slugs and snails that would otherwise bedevil gardeners and making them even more remarkable.

Wet lawn woes

We all have them. All this moisture and humidity has our turf grasses growing rapidly and happily. One nice side effect is that all this rain is helping our cool-season lawn grasses to better handle the summer heat, which means fewer chances for weeds to move in.

But grasses can be severely damaged if they are cut when wet, and right now it seems like they are always wet. So what’s a mower to do? As it is with comedy, timing is everything.

Try and wait until we have gone a few days without rain, and try to cut later in the day when the grass will be drier. If your grass has gotten really high, don’t try and reduce it all in one shot. Take an inch off the top now and another inch in a few days.

Get a new blade for your mower or have the old one sharpened, even if you started the season with a new or newly-sharpened blade. A super-sharp blade is much kinder to slightly damp sod.

Evicting moles takes a multi-step approach

Minister Robert in Prince George’s County writes: “I have mole trails and hills in parts of my yard. Can you tell me how to get rid of them?”

Moles are tough characters to evict.

The first thing you want to try is spreading or spraying a castor oil repellent on the lawn. Widely available in both wet and dry formulations under names like “Mole-Med,” “Mole-Max” and (my favorite, at least for its name) “Mole-Atov Cocktail,” almost every garden supply company now sells one of these non-toxic mole (and vole) repellents. Choose products that have the highest concentration of castor oil as the active ingredient.

Then apply milky spore powder to your lawn in August or September to safely eliminate the grubs that moles feed on underground. Non-toxic to everything other than grubs, milky spore only works when applied in the late summer or early fall, not in the spring. Then use a castor oil repellent again early next spring, level out any remaining tunnels and fill in any holes.

If new tunnels and holes appear in your lawn after that, the only answer is spring-loaded (‘deadly’) traps, or to rescue a ‘ratting’ dog like a Jack Russell terrier. No moles or voles will set up housekeeping when a terrier has access to the lawn.

Don’t use poisons, which don’t work because moles won’t eat them; mothballs, which don’t work and are highly toxic to you, pets, children and the rest of the planet; or vibrating devices, which simply don’t work.

Yellow lower leaves on tomatoes

Jim down in Huntingtown writes: “The lower leaves on my tomato plants are turning yellow. Will coffee grounds help? The garden has sandy soil that I have been putting top soil and leaf mulch in.”

If you’ve been planting your tomatoes in the same spot year after year, the plants are showing the first signs of verticillium wilt, a soil-borne disease with no cure other than planting your tomatoes somewhere else for the next few years.

Yellow leaves can be a sign of a nutritional deficiency, but that would affect all the leaves and show up on your other plants as well. That said, sandy soil requires more nutrients than clay soil, so stop adding nutrition-less topsoil and go heavy on the compost, which is what I presume you mean by ‘leaf mulch.’

Coffee grounds are not an all-purpose fertilizer. Highly acidic and nitrogen-rich coffee grounds should only be used directly on acid-loving plants, and even then, not when the plants are forming flowers, buds or fruits, as nitrogen produces big plants with few flowers.

Sandra and the giant peach

Sandra in Gainesville writes: “We planted a peach tree too close to our fence three years ago. It is now about 16-feet-tall. We would like to try digging it up and moving it to another location. Is this doable for DIYers?”

I certainly wouldn’t attempt it. To be successful with a 16-foot-tall tree, you’d have to unearth and then move a rootball weighing several hundred pounds. Plus, you clearly have what’s called a ‘standard’ peach tree, and their height makes essential tasks like pruning, thinning, and (if you’re lucky) harvesting difficult and dangerous, no matter where it is located.

I would cut that monster down and replace it with a couple of disease-resistant dwarf varieties that will top out at around 6 to 8 feet in height. You always get better fruit with two or more trees and shorter trees are much easier to care for. They also don’t outgrow their space.